According to the datasheet: https://www.st.com/resource/en/datasheet/lsm303agr.pdf (p.13) the accuracy at any sensitivity is +-7%. At rest you should expect an acceleration magnitude of 1.0 +-7% or anything between 0.93...1.07. Where the magnitude is = sqrt(x*x + y*y + z*z)

Those values seem within those limits.

Edit: Actually, I think the "Linear acceleration zero-g level offset accuracy" (also p.13) of +-80mg is the more relevant figure.